The present invention relates generally to multicylinder two-cycle engines and relates more particularly to a wrist pin lubrication system for such engines.
In the type of two-cycle engine wherein the air/fuel charge is compressed within the crankcase preparatory to entry into the combustion chamber, lubrication of the crankshaft, crank and wrist pin bearings as well as the piston and cylinder is provided by a lubricant added to the fuel. The mixture of fuel and lubricant enters the crankcase as a mist which penetrates into the bearing regions and provides lubrication to the moving parts.
The wrist pin bearing, due to its location within the reciprocating piston as well as centrifugal effects, may not receive an adequate amount of lubricant, especially with the high fuel-lubricant ratios of modern engines. As a result, undue friction, wear and a potential for wrist pin bearing failure may occur with conventional two-cycle engine lubrication systems. Efforts to improve the penetration of the mist into the wrist pin bearing have included a hole or series of holes, or slots in the connecting rod to direct the fuel/lubricant mist toward the wrist pin bearing. However, centrifugal forces produced by the high speed movement of the connecting rod inhibits lubricant movement toward the wrist pin region.